1. Field of the Invention
The present invention relates to a cleaning blade, a process cartridge and an electrophotographic apparatus that include the cleaning blade, and a polyester urethane rubber.
2. Description of the Related Art
Generally, when a toner image formed on the surface (outer peripheral surface) of an electrophotographic photosensitive member (hereinafter, referred to simply as “photosensitive member”) is transferred to a transfer material or an intermediate transfer material, and when the toner image is further transferred from the intermediate transfer material to a transfer material, a portion of the toner (developer) is likely to remain on the surface of the photosensitive member or the intermediate transfer material. Accordingly, it is necessary to remove the toner remaining on the surface of the photosensitive member or the intermediate transfer material (hereinafter, referred to as “untransferred residual toner”). Generally, untransferred residual toners are removed using a cleaning blade.
A urethane rubber has been commonly used as a cleaning blade because a urethane rubber realizes high abrasion resistance, small permanent deformation, and the like.
Commonly, a cleaning blade is disposed so that the edge portion of the cleaning blade comes into contact with a member to be cleaned (e.g., a photosensitive member or an intermediate transfer material). A toner remaining on the surface of the member to be cleaned is scraped off with the edge portion of the cleaning blade due to the friction between the cleaning blade and the member to be cleaned and then removed from the surface of the member to be cleaned. Therefore, a friction force is generated between the cleaning blade and the member to be cleaned. A large friction force is likely to pose a risk of, for example, curling of the cleaning blade.
Japanese Patent No. 3239607 (hereinafter, referred to as “PTL 1”) describes a technique of reducing the friction at a contact portion of a cleaning blade at which the cleaning blade comes into contact with a member to be cleaned by applying a siloxane compound including both a reactivity component that reacts with a urethane rubber and a lubricity component onto the inner surface of a mold used for producing the cleaning blade made of a urethane rubber and then causing the siloxane compound to adhere to the surface of the prepared (molded) urethane rubber.
Japanese Patent Laid-Open No. 2001-75451 (hereinafter, referred to as “PTL 2”) describes a technique of reducing the friction at a contact portion of a cleaning blade at which the cleaning blade comes into contact with a member to be cleaned by controlling the concentration of isocyanurate groups (isocyanurate linkages) in the surface of the edge portion of the cleaning blade made of a urethane rubber to be higher than the concentration of isocyanurate groups inside the cleaning blade.
When a siloxane compound is attempted to be attached onto the surface of a urethane rubber (cleaning blade made of a urethane rubber), a siloxane compound is less likely to adhere to the surface of a urethane rubber because of the low wettability of urethane rubber. Thus, it has been difficult to realize high lubricity.
Accordingly, in the technique described in PTL 1, the adhesion between a urethane rubber and a siloxane compound is increased by adding a reactivity component that reacts with a urethane rubber to the siloxane compound.
However, as a result of studies conducted by the inventors of the present invention, it was found that, when a siloxane compound having reactivity with a urethane rubber is used, a urethane rubber may reduce the mobility of the siloxane compound, which prohibits high lubricity from being realized.
When the concentration of isocyanurate groups in the surface of the edge portion of the cleaning blade is increased as in the technique described in PTL 2, the hardness of the edge portion tends to be increased. If the hardness of the edge portion is excessively high, the cleaning blade is less capable of following the unevenness of the surface of a member to be cleaned, which increases the risk of faulty cleaning. Faulty cleaning is likely to occur particularly during cleaning of a toner having a small particle size.